Precise measurement of the e+ e- to pi+ pi- (gamma) cross section with the Initial State Radiation method at BABAR

TL;DR

This paper reports a highly precise measurement of the e+ e- to pi+ pi- (gamma) cross section using the ISR method at BABAR, significantly contributing to the calculation of the muon magnetic anomaly.

Contribution

It provides the most accurate cross section measurement from threshold to 1.8 GeV using ISR at BABAR, improving the precision of the muon g-2 theoretical prediction.

Findings

Hadronic contribution to muon g-2: (514.1 +- 2.2(stat) +- 3.1(syst)) x 10^{-10}

Cross section measured from threshold to 3 GeV with high precision

ISR method effectively determines the e+ e- to pi+ pi- cross section

Abstract

A precise measurement of the cross section of the process e+ e- to pi+ pi- (gamma) from threshold to an energy of 3 GeV is obtained with the initial state radiation (ISR) method using 232 fb^-1 of data collected with the BABAR detector at e+ e- center-of-mass energies near 10.6 GeV. The ISR luminosity is determined from a study of the leptonic process e+ e- to mu+ mu- gamma (gamma). The leading-order hadronic contribution to the muon magnetic anomaly calculated using the pi pi cross section measured from threshold to 1.8 GeV is (514.1 +-2.2(stat} +-3.1(syst}) x 10^{-10}.